Sheet Rock.RTM., also called wallboard, drywall, plasterboard and gypsum board, is manufactured panel used for rapid and efficient construction of interior walls of buildings. A typical wallboard panel comprises a pressed gypsum (calcium sulfate) board sandwiched between sheets of smooth, strong cardboard and paper. When wallboard is applied to walls, metal corner beads are often used for quickly and easily constructing outside corners. A familiar commercial corner bead product comprises a length of light gage angle iron strip which is bent to a 90 degree included angle. When making a typical right angle wallboard wall outside corner, the wallboard mechanic nails or screws the corner bead over the corner joint which formed by two intersecting pieces of wallboard, previously fastened to the wall. Then, the mechanic applies one or more layers of a thick aqueous paste of gypsum or other ceramic powder, commonly called joint compound, over the corner bead and adjacent wallboard. The resultant corner has good definition and appearance, and good provides resistance to damage when objects hit the corner during use of the building.
Manufactures of corner beads typically supply them with a 90 degree included angle, since that is the angle of most corners meet in buildings. However, when there is a corner in a building wall having an included angle greater than 90 degrees, for instance 135 degrees, the wallboard finisher will either forgo the use of a corner bead or re-shape a 90 degree angle bead. Since it is preferable to have some sort of corner bead, the typical approach is to re-shape a common 90degree angle bead. Mechanics typically accomplish such by lying the bead on a flat surface, such as a floor or table, so its legs are facing upward and the apex is down on the surface. Then, by lightly hammering along the length of the bead, the legs are spread, or splayed apart. Doing this takes time and can result in an imperfect or uneven job. Even a skilled mechanic might deform the corner bead more or less than the desired amount; or might vary the degree of splaying along the length of the bead. Because the legs of a corner bead are perforated, the corner bead has an uneven stiffness from point to point along its length. That distinguishes it from a common piece of angle iron strip and makes the deformation of the legs less uniform and predictable.
Of course, factories are capable of manufacturing corner beads with other-than-90 degree included angles and some about-133 degree angle beads are commercially available. But, a variety of such beads is not commonly available. And, because non-90 degree angle corner beads are used relatively infrequently, mechanics will avoid stocking such items. Thus, there is a need for a way to quickly, easily and accurately alter the dimension of conventional 90 degree angle corner bead in the field, using a tool which is convenient and reasonable in cost